Metal Foil and Composite Heat Dissipating Plate Thereof

ABSTRACT

The present invention provides a highly thermal conductive and heat radiation absorptive metal foil with a basis weight of at least 220g/m 2  and a metal content of at least 90%. The present invention further provides a composite heat dissipating plate comprising a metal foil having a first surface and an opposite second surface, a basis weight of at least 220g/m 2 , a metal content of at least 90%, and at least a layer of nitrogen-doped graphene coated on at least one of the first surface and the second surface. At least one of the above-mentioned surfaces has a roughness of 0.19≦Ra≦0.23 μm, 1.3≦Rt≦1.84 μm and/or 1.02≦Rz≦1.07 μm. The metal foil has crystal size between 308 and 434 Å, and a lightness of surface colors of 25&lt;L*&lt;40.

CROSS REFERENCE OF RELATED APPLICATION

This Non-provisional application claims priority under 35 U.S.C. §119(a) on patent application Ser. No. 10/4,120,046 filed in Taiwan on Jun. 22, 2015, the entire contents of which are hereby incorporated by reference.

NOTICE OF COPYRIGHT

A portion of the disclosure of this patent document contains material which is subject to copyright protection. The copyright owner has no objection to any reproduction by anyone of the patent disclosure, as it appears in the United States Patent and Trademark Office patent files or records, but otherwise reserves all copyright rights whatsoever.

BACKGROUND OF THE PRESENT INVENTION

Field of Invention

The present invention relates to a metal foil and a composite heat dissipating plate thereof, more particularly, to a composite heat dissipating plate comprising a metal foil with an excellent heat dissipating performance.

Description of Related Arts

An increasing demand in heat dissipating for electronic components is driving the demand for heat dissipating materials in recent years. Existing common heat dissipating materials may be classified in two categories: metal and non-metal. Metal materials have various advantages including good heat dissipation, ease of acquisition, ease of machining, and low material costs, and hence have become the most common heat dissipating materials. The most common metal materials include copper foil, aluminum foil, gold foil and silver foil. However, electronic products are becoming more and more sophisticated due to the increasing complexity thereof, so that the power consumption of the electronic component becomes relatively high and conventional heat dissipating materials can no longer meet the heat dissipating demands. Therefore, a new metal material with high thermal conductivity and high heat radiation absorption is urgently required.

SUMMARY OF THE PRESENT INVENTION

The object of the present invention is to provide a highly thermal conductive and heat radiation absorptive metal foil and a composite heat dissipating plate thereof that are suitable for continuous industrial productions. Materials of the metal foil may be selected from at least one of copper, aluminum, copper alloy and aluminum alloy, but not limited hereto in the present invention. In embodiments of the present invention, copper foil is selected as the material, and the basis weight, copper content and surface roughness thereof are altered to obtain a copper foil with high thermal conductivity and heat radiation absorption, and a composite heat dissipating plate structure of the same. The copper foil may be a rolled copper foil or an electrolytic copper foil, and the basis weight, copper content and surface roughness thereof are altered before being proceed to fabricate the composite heat dissipating plate. Such alterations change thermal conductive characteristics of the copper foil, the roughness on the surface increases the surface area so that the heat radiation absorption is higher, and a larger contact surface and bonding strength to at least one nitrogen-doped graphene coating or other coating layers. These simple alterations maximize the thermal conductivity of the copper foil and the composite heat dissipating plate thereof.

Another object of the present invention is to provide metal foils of different basis weights and copper contents, and heat dissipating plates thereof. Materials of the metal foil may be selected from at least one of copper, aluminum, copper alloy and aluminum alloy, but not limited hereto in the present invention. The metal foil is a copper foil in embodiments of the present invention. A double sided tape may be used to attach the copper foil or the composite heat dissipating plate to a base material of a testing fixture, so that the copper foil or the composite heat dissipating plate may be positioned towards a heat source to absorb heats generated by a central processing unit (CPU) or a battery pack. The heats are directed away from the heat source through thermal conduction or thermal radiation to prevent a reduced battery performance or damages to electronic components due to accumulated heats in electronic products.

For above objects, the present invention provides a metal foil with a basis weight of at least 220 g/m² and a metal content of at least 90%.

The metal foil aforementioned is a copper foil.

The metal foil aforementioned has a basis weight between 220 to 884 g/m².

The metal foil aforementioned has a metal content of at least 98%.

The metal foil aforementioned has a first surface and an opposite second surface, and at least one of the above-mentioned surfaces has a roughness of 0.19≦Ra≦0.23 μm.

The metal foil aforementioned has a first surface and an opposite second surface, and at least one of the above-mentioned surfaces has a roughness of 1.3 ≦Rt≦1.84 μm.

The metal foil aforementioned has a first surface and an opposite second surface, and at least one of the above-mentioned surfaces has a roughness of 1.02≦Rz≦1.07 μm.

The metal foil aforementioned has crystal size between 308 and 434 Å.

The metal foil aforementioned has a lightness of surface colors of 25<L*<40.

The present invention further provides a composite heat dissipating plate with a metal foil which having a first surface and an opposite second surface, wherein the metal foil has a basis weight of at least 220 g/m², a metal content of at least 90%, and at least a layer of nitrogen-doped graphene coated on at least one of the first surface and the second surface.

The metal foil of the composite heat dissipating plate aforementioned is a copper foil.

The metal foil of the composite heat dissipating plate aforementioned has a basis weight between 220 to 884 g/m².

The metal foil of the composite heat dissipating plate aforementioned has a metal content of at least 98%.

The metal foil of the composite heat dissipating plate aforementioned has a preferred roughness of 0.19≦Ra≦0.23 μm on at least one of the first surface and the second surface.

The metal foil of the composite heat dissipating plate aforementioned has a preferred roughness of 1.3≦Rt≦1.84 μm on at least one of the first surface and the second surface.

The metal foil of the composite heat dissipating plate aforementioned has a preferred roughness of 1.02≦Rz≦1.07 μm on at least one of the first surface and the second surface.

The metal foil of the composite heat dissipating plate aforementioned has crystal size between 308 and 434 Å.

The metal foil of the composite heat dissipating plate aforementioned has a lightness of surface colors of 25<L*<40.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features and advantages of the present invention will be apparent from the following detailed description of the embodiments of the invention in conjunction with the accompanying drawings, in which:

FIG. 1 is a schematic illustration of a structure of a copper foil according to basis for comparison, comparing samples 1 to 7, and embodiments 1 to 12 of the present invention;

FIG. 2 is a schematic illustration of a structure of a composite heat dissipating plate according to embodiment 13 of the present invention;

FIG. 3 is a schematic illustration of a structure of a composite heat dissipating plate according to embodiment 14 of the present invention;

FIG. 4 is a schematic illustration of a testing fixture for the copper foil according to basis for comparison, comparing samples 1 to 7, and embodiments 1 to 12 of the present invention;

FIG. 5 is a schematic illustration of a testing fixture for the composite heat dissipating plate according to embodiment 13 of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The present invention is explained in relation to its embodiments and comparing samples. Any person of ordinary skill in the art shall understand methods disclosed in the present invention and appreciate advantages and benefits other than mentioned therein. It is to be understood that many other possible modifications and variations can be made without departing from the spirit and scope of the invention as hereinafter claimed.

The following description discloses various thicknesses, basis weights, copper contents and surface roughnesses of a copper foil, and compares effects in thermal conductivities thereof. The copper foil has a thickness between 14 and 100 μm, a basis weight between 124 and 884 g/m², and a preferred basis weight between 220 and 884 g/m². The copper content of a copper foil is calculated according to formula: copper content (%)=copper basis weight (g/m²)÷ copper density 8.96 (g/m²)× copper thickness (μm), wherein a copper content of at least 90% is preferred and a copper foil with 98% copper content is the most preferred.

According to the present invention, the copper foil has a first surface and an opposite second surface, and at least one of the above-mentioned surfaces has a roughness of 0.19≦Ra≦0.23 μm, 1.3≦Rt≦1.84 μm and/or 1.02≦Rz≦1.07 μm. The roughness may be a naturally formed rough structure on ordinary copper foil (sometimes referred as rolled copper foil), electrolytic processed (sometimes referred as electrolytic copper foil), or through other ordinary techniques of forming rough structures on copper foil or other metals, but not limited thereto in the present invention.

According to present invention, the copper foil is a rolled copper foil with a naturally formed roughness, an electrolytic copper foil with a roughness formed with existing electrolytic methods, or other copper foils with roughness and not limited thereto in the present invention. However, certain values of basis weight and copper content are required for the rolled copper foil and electrolytic copper foil to achieve a preferred heat dissipating performance. Values of Ra, Rt and Rz are different when roughness on rolled copper foil and electrolytic copper foil are different. If values of Ra, Rt and Rz are too high, the basis weight and copper content are insufficient and resulting a poor heat dissipating performance. Ra, Rt and Rz represent different surface roughness measuring methods in surface profile measurement. Ra represents an arithmetic average of absolute values, that is the average of absolute values of the vertical deviations of the roughness profile from the mean line. Rt represents a maximum height of the profile, that is the distance between the highest peak and lowest valley in each sampling length. Rz represents a 10 (ten) points average roughness, that is the average distance between 5 (five) highest peak and 5 (five) lowest valley in each sampling length.

In the present invention, the copper foil further has various crystal size and lightnesses of surface colors. Crystal size are crystallinities of the copper foil which may be defined by using X-ray diffraction or other methods of defining crystal size of metal foils. Lightnesses of surface colors are scales of perceived color characteristics of copper foil surfaces. The L*a*b color space developed by International Commission on Illumination (CIE) in 1976, or CIE 1976 color space, has been adopted as an industrial standard to precisely describe colors and lightness, wherein, L* indicates lightness, a* and b* indicate color opponent dimensions. L* is used to indicate lightness of surface color of the copper foil in the present invention.

In present invention, a layer of nitrogen-doped graphene (referred as N-graphene hereafter) is applied on at least one of the first surface or the second surface of the copper foil by coating or other applying methods. The N-graphene may be prepared by doping nitrogen into graphene, wherein the graphene may be obtained through mechanical exfoliation, oxidation reduction, or electrochemical methods, and not limited thereto in the present invention. The graphene may be selected from at least one of monolayer graphene, multilayer graphene, graphene oxide, reduced graphene oxide and graphene derivatives, and not limited thereto in the present invention.

FIGS. 1 and 4 are schematic illustrations of structures of a copper foil and a testing fixture according to the basis for comparison, comparing samples 1 to 7, and embodiments 1 to 8 of the present invention. As illustrated, the copper foil 101 has a first surface 112 and an opposite second surface 113. The present invention provides a temperature testing method with following steps: applying a double sided tape 103 or other adhesive materials on the second surface 113 of the copper foil 101, attaching the copper foil 101 together with the double sided tape 103 on a base material 106, and then placing in the testing fixture for temperature tests. The testing fixture may be regarded as a simulation of a tablet PC, wherein a heating chip 107 of one square centimeter (1×1 cm²) in size is attached to a copper plate 105 to simulate an operating a central processing unit (CPU), and a tin foil 111 attached thereunder is to simulate other electrical parts of the tablet PC. The testing fixture has three sensing spots for temperature tests, namely a thermal spot 110 on the heating chip 107, a first testing spot 108 on the base material 106 on top of the heating chip 107, and a second testing spot 109 which is also on the base material 106 and 0.5 (zero point five) to 5 (five) centimeters apart from the first testing spot 108. The temperature testing method measures the gap between a temperature difference T1 (° C.)(as basis value) and another temperature difference T2 (° C.), wherein the temperature difference T1 is measured between the first testing spot 108 and the second testing spot 109 of the copper foil 101 of the basis for comparison, and the temperature difference T2 is measured between the first testing spot 108 and the second testing spot 109 of the copper foil 101. In this embodiment, the horizontal distance between the first testing spot 108 and the second testing spot 109 is 0.5 (zero point five) centimeter, but not restricted thereto in other embodiments of the present invention. Testing results are shown in Table 1. With reference to FIG. 4, the temperature on the thermal spot 110 is higher than the temperature on the first testing spot 108, and the temperature on the first testing spot 108 is higher than the temperature on the second testing spot 109. Heats are effectively directed away from the heating chip 107 when the copper foil 101 has a good heat dissipating performance, the temperature on the first testing spot 108 and the temperature on the second testing spot 109 are closer as a result. The temperature difference T2 between the first testing spot 108 and the second testing spot 109 of the copper foil 101 is smaller, the temperature difference T1 between the first testing spot 108 and the second testing spot 109 of the copper foil 101 of the basis for comparison is larger, hence T1(° C.) is greater than T2(° C.). Therefore, a positive value of T1 minus T2 indicates a good heat dissipating performance of the copper foil 101, where the greater the value, the better the heat dispatching performance.

With reference to Table 1, embodiment 5 is a result of additional 184.33 g/m² copper basis weight on comparing sample 4, and has a copper content of 98.3%, Ra of 0.19 μm, Rt of 1.3 μm, Rz of 1.07 μm. The heat dissipating performance of embodiment 5 is 2.24° C. higher as compared to comparing sample 4. Therefore, the heat dissipating performance of the copper foil improves with an increased copper basis weight. In addition, comparing sample 5 is a result of additional 41.67 g/m² copper basis weight and less 20.2% copper content on embodiment 5, and has a copper basis weight of 350 g/m², copper content 78.1%, Ra of 0.19 μm, Rt of 1.44 μm, Rz of 1.02 μm. The heat dissipating performance of comparing sample 5 is 0.428° C. lower than embodiment 5. Therefore, aside from the copper basis weight, the copper content also affects the heat dissipating performance. Comparing samples 1 to 7 and embodiments 1 to 8 clearly indicate that the copper foil 101 has better heat dissipating performances when the basis weight is at least 220 g/m² and the copper content is at least 90%. In embodiments 1 to 8, copper foil 101 has a roughness of 0.19≦Ra≦0.23 μm, 1.3≦Rt≦1.84 μm and/or 1.02 ≦Rz≦1.07 μm on at least one of the first surface and the second surface.

TABLE 1 Copper Foil Thick- Basis Copper ness Weight Content T1-T2 (μm) (g/m²) (%) (° C.) Ra Rt Rz Basis for 35 309 98.5 0 0.19 1.4 1.02 Comparison Comparing 35 180 57.4 −3.247 0.19 1.4 1.02 Sample 1 Comparing 35 240 76.5 −3.101 0.19 1.4 1.02 Sample 2 Comparing 35 280 89.3 −2.338 0.19 1.4 1.02 Sample 3 Comparing 14 124 98.8 −2.04 0.19 1.4 1.02 Sample 4 Comparing 50 350 78.1 −0.228 0.19 1.4 1.02 Sample 5 Comparing 18 158.1 98 −1.74 0.19 1.3 1.07 Sample 6 Comparing 25 219.52 98 −1.043 0.19 1.3 1.07 Sample 7 Embodiment 50 442 98.7 1.056 0.19 1.4 1.02 1 Embodiment 70 619 98.7 1.396 0.19 1.4 1.02 2 Embodiment 80 707 98.6 1.613 0.19 1.4 1.02 3 Embodiment 100 884 98.6 1.74 0.19 1.4 1.02 4 Embodiment 35 308.33 98.3 0.2 0.19 1.3 1.07 5 Embodiment 50 439.04 98 1.242 0.19 1.3 1.07 6 Embodiment 70 614.66 98 1.622 0.19 1.3 1.07 7 Embodiment 35 313.53 99.98 0.2 0.23 1.84 1.06 8

FIGS. 1 and 4 are schematic illustrations of structures of a copper foil and a testing fixture according to embodiments 9 to 12 of the present invention. As illustrated, the copper foil 101 has a first surface 112 and an opposite second surface 113. The copper foil 101 used in embodiments 9 to 12 has the same copper basis weight of 313.53 g/m², copper content of 99.98% and copper foil thickness of 35 μm. The same temperature testing method to the basis for comparison, comparing samples 1 to 7, and embodiments 1 to 8 is applied. The gap between the temperature difference T1 of the copper foil 101 of the basis for comparison (as basis value) and the temperature difference T2 of the copper foil 101 of embodiments 9 to 12 is tested. The testing fixture is as shown in FIG. 4 and the results are shown in Table 2. T1 minus T2 values of embodiments 9 to 12 are all positive which indicates better heat dissipating performances. The copper foil 101 have crystal size between 308 and 434 Åand/or lightness of surface colors of 25<L*<40.

TABLE 2 Copper Foil Basis Copper Embod- Thickness Weight Content crystal size T1-T2 iment (μm) (g/m²) (%) (Å) Lightness (° C.) 9 35 313.53 99.98 345.987 39.32 0.1 10 35 313.53 99.98 308.462 25.84 0.2 11 35 313.53 99.98 433.726 35.87 0.2 12 35 313.53 99.98 393.82 39.32 0.2

FIGS. 2 and 5 are schematic illustrations of the composite heat dissipating plate and the testing fixture of embodiment 13. As illustrated, a composite heat dissipating plate 100 includes a copper foil 101 having a first surface 112, an opposite second surface 113, and a layer of N-graphene 102 coated on the first surface 112 of the copper foil 101. The copper foil 101 has a copper basis weight of 308.33 g/m², a copper content of 98.3%, and a copper foil thickness of 35 μm. The layer of N-graphene 102 has a nitrogen content of 3.92 wt %, coating thickness of 15 μm, and is coated on a single side. The present invention provides a temperature testing method including following steps: applying a double sided tape 103 or other adhesive materials on the second surface 113 of the copper foil 101 of the composite heat dissipating plate 100, attaching the composite heat dissipating plate 100 together with the double sided tape 103 onto the base material 106, and then placing in the testing fixture for temperature tests. The testing fixture may be regarded as a simulation of a tablet PC, wherein a heating chip 107 of one square centimeter (1×1 cm²) in size is attached to the copper plate 105 to simulate an operating CPU, and a tin foil 111 attached thereunder is to simulate other electrical parts of the tablet PC. The testing fixture has 3 (three) sensing spots to detect temperatures, namely a thermal spot 110 on the heating chip 107, a first testing spot 108 on the base material 106 on top of the heating chip 107, and a second testing spot 109 which is also on the base material 106 and 0.5 (zero point five) to 5 (five) centimeters apart from the first testing spot 108. The temperature testing method measures the gap between a temperature difference T1 (° C.) (as basis value) and another temperature difference T2 (° C.), wherein the temperature difference T1 is measured between the first testing spot 108 and the second testing spot 109 of the copper foil 101, and the temperature difference T2 is measured between the first testing spot 108 and the second testing spot 109 of the composite heat dissipating plate 100, and the first testing spot 108 is 0.5 centimeters apart from the second testing spot 109. Testing results are shown in Table 3. With reference to FIG. 5, the temperature on the thermal spot 110 is higher than the temperature on the first testing spot 108, and the temperature on the first testing spot 108 is higher than the temperature on the second testing spot 109. Heats are effectively directed away from the heating chip 107 when the composite heat dissipating plate 100 has a good heat dissipating performance, the temperature on the first testing spot 108 and the temperature on the second testing spot 109 are closer as a result. The temperature difference T2 between the first testing spot 108 and the second testing spot 109 of the composite heat dissipating plate 100 is smaller, the temperature difference T1 between the first testing spot 108 and the second testing spot 109 of the copper foil 101 is larger, hence T1(° C.) is greater than T2(° C.). Therefore, a positive value of T1 minus T2 indicates a good heat dissipating performance of the composite heat dissipating plate 100, where the greater the value, the better the heat dissipating performance.

FIG. 3 is a schematic illustration of a structure of a composite heat dissipating plate according to embodiment 14 of the present invention. As illustrated, the composite heat dissipating plate 200 includes a copper foil 101 having a first surface 112, an opposite second surface 113, and 2 (two) layers of N-graphene 102 respectively coated on the first surface 112 and the second surface 113 of the copper foil 101. The copper foil 101 has a copper basis weight of 309 g/m², a copper content of 98.5% and a copper foil thickness of 35 μm. The 2 (two) layers of N-graphene 102 have a nitrogen content of 3.92 wt %, coating thickness of 65 μm, and coated on double sides of the copper foil 101. The same temperature testing method to embodiment 13 is applied and the testing fixture is as shown in FIG. 5. The only difference is that the composite heat dissipating plate 100 of embodiment 13 is replaced by a heat dissipating plate 200 in embodiment 14, and the results are shown in Table 3.

With reference to Table 3, T1 minus T2 values are all positive in embodiments 13 and 14, which indicates that better heat dissipating performances are achieved regardless the layer of N-graphene 102 is coated on a single side (the composite heat dissipating plate 100) or on double sides (the composite heat dissipating plate 200). In embodiments 13 and 14, the copper foil 101 has a first surface 112 and an opposite second surface 113, and at least one of the surfaces has a roughness of Ra of 0.19 μm, 1.3≦Rt≦1.44 μm and/or 1.02≦Rz≦1.07 μm.

TABLE 3 Copper Foil Thickness/ N- Cop- Graphene per Em- Film N- Basis Con- bodi- Thickness Graphene Weight tent T1-T2 ment (μm) Coating (g/m²) (%) (° C.) Ra Rt Rz 13 35/15 Single 308.33 98.3 2.7 0.19 1.3 1.07 14 35/65 Double 309 98.5 1.9 0.19 1.44 1.02 

What is claimed is:
 1. A metal foil having a basis weight of at least 220 g/m² and a metal content of at least 90%.
 2. The metal foil of claim 1, wherein said metal foil is a copper foil.
 3. The metal foil of claim 1, wherein said metal foil has a basis weight between 220 and 884 g/m².
 4. The metal foil of claim 1, wherein said metal foil has a metal content of at least 98%.
 5. The metal foil of claim 1, wherein said metal foil has a first surface and an opposite second surface; and at least one of said first surface and said second surface has a roughness of 0.19≦Ra≦0.23 μm.
 6. The metal foil of claim 1, wherein said metal foil has a first surface and an opposite second surface; and at least one of said first surface and said second surface has a roughness of 1.3≦Rt≦1.84 μm.
 7. The metal foil of claim 1, wherein said metal foil has a first surface and an opposite second surface; and at least one of the said first surface and said second surface has a roughness of 1.02≦Rz≦1.07 μm.
 8. The metal foil of claim 1, wherein said metal foil has crystal size between 308 and 434 Å.
 9. The metal foil of claim 1, wherein said metal foil has a lightness of surface colors of 25<L*<40.
 10. A composite heat dissipating plate including: a metal foil having a first surface and an opposite second surface, wherein said metal foil has a basis weight of at least 220 g/m² and a metal content of at least 90%; and at least one layer of nitrogen-doped graphene applied on at least one of said first surface and said second surface of said metal foil.
 11. The composite heat dissipating plate of claim 10, wherein said metal foil is a copper foil.
 12. The composite heat dissipating plate of claim 10, wherein said metal foil has a basis weight between 220 and 884 g/m².
 13. The composite heat dissipating plate of claim 10, wherein said metal foil has a metal content of at least 98%.
 14. The composite heat dissipating plate of claim 10, wherein at least one of said first surface and said second surface has a roughness of 0.19≦Ra≦0.23 μm.
 15. The composite heat dissipating plate of claim 10, wherein at least one of said first surface and said second surface has a roughness of 1.3≦Rt≦1.84 μm.
 16. The composite heat dissipating plate of claim 10, wherein at least one of said first surface and said second surface has a roughness of 1.02≦Rz≦1.07 μm.
 17. The composite heat dissipating plate of claim 10, wherein said metal foil has crystal size between 308 and 434 Å.
 18. The composite heat dissipating plate of claim 10, wherein said metal foil has a lightness of surface colors of 25<L*<40. 